The mechanisms which generate the movements of the lobster's stomach serve as a model system of cyclic motor output. We will first describe these normal movements using a) cinematographic analysis; b) chronic recordings of EMGs from stomach musculature. The stomatogastric ganglion generates two independent cyclic motor patterns. To find how these patterns are generated, we will characterize each neuron in the ganglion, and analyze the network which these neurons form by: a) completing the demonstrated network of synaptic connections; b) recording from neuropilar processes of known neurons; c) studying the structure of identified neurons and correlating their structure with their physiological properties; d) determining the ionic mechanisms of the chemical synapses; e) examining the control of electrotonic coupling between by chemical synapses. We have two hypothesis about the mechanisms which generate the motor patterns, and will test them by: a) experimentally interfering with spontaneous activity in particular neurons; b) determining whether individual neurons can burst in isolation. We will study the influence of sensory feedback, and of command fibers originating in the central nervous system. The physiological experiments outlined above are the core of this proposal. We have in addition, two related projects which reinforce the physiological study and for which we request modest support: a) transmitter chemistry; b) digital modeling of the known network of synaptic connections.